Technical Field
The present invention relates to a magnetoresistive device, a magnetoresistive random access memory (MRAM) using the magnetoresistive device, and a magnetic recording method.
Background Art
A magnetic memory, a magnetic random access memory or a magnetoresistive random access memory (MRAM), is a limitlessly rewritable nonvolatile memory, now being substituted for SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory), NOR-Flash or the like. The substitution of MRAM for SRAM, DRAM or the like allows a reduction of power consumption because MRAM stores information in a nonvolatile manner.
Non-Patent Literature 1 discloses that, among MRAM, a three-terminal MRAM having a three-terminal cell structure has a circuit structure suitable for high-speed operation and thus is capable of high-speed operation of the same level as current SRAM.
Non-Patent Literature 2 discloses that, among three-terminal MRAM, a three-terminal domain wall motion MRAM using electrical current-induced domain wall motion is suitable for application to leading-edge LSI generation because it allows reduction of a write current and writing speed with a decrease in device size.
Non-Patent Literature 3 discloses that MRAM with a small write current and high heat stability is provided by use of a material with a perpendicular magnetic anisotropy for a layer where writing using current induced domain wall motion is done.
In a three-terminal domain wall motion MRAM, it is desirable that an electric current required for driving a domain wall by means of an electric current is small and a domain wall motion speed is high.
Non-Patent Publications 4, 5 and 6 experimentally and technically disclose that a domain wall (DW) can move at high speed with a small electric current when a spin current flows, by the spin Hall effect, from a layer contacting the domain wall whose rotational direction is substantially determined by the Dzyaloshinskii-Moriya interaction.